SQL查詢多行

Question

我有一個看起來像這樣的表：

---------------------------
|housing_id | facility_id |
---------------------------
|    1      |      7      |
|    1      |      4      |
|    2      |      7      |
---------------------------

現在，我要執行的操作是獲取具有兩位7和4的facility_id的所有housing_id。因此，在這種情況下，查詢應僅返回housing_id 1。 數據庫是mysql。

Answer 1

另一種方法是-

SELECT housing_id
FROM mytable
WHERE facility_id IN (4,7)
GROUP BY housing_id
HAVING COUNT(DISTINCT facility_id) = 2

更新 -受約瑟夫（Josvic）評論的啟發，我決定進行更多測試，並認為我將包括我的發現。

使用此查詢的好處之一是很容易進行修改以包含更多的facility_id。 如果您要查找所有具有facility_ids 1、3、4和7的housing_id，則只需-

SELECT housing_id
FROM mytable
WHERE facility_id IN (1,3,4,7)
GROUP BY housing_id
HAVING COUNT(DISTINCT facility_id) = 4

根據所采用的索引策略，所有這三個查詢的性能差異很大。 無論使用何種索引，我都無法從依賴子查詢版本中獲得測試數據集上的合理性能。

如果在兩列上使用單獨的單列索引，Tim提供的自連接解決方​​案將表現非常出色，但是隨着標准數量的增加，它的表現將不盡人意。

這是我測試表上的一些基本統計信息-50萬行-147963房屋ID，idacity_id的潛在值在1到9之間。

這是用於運行所有這些測試的索引-

SHOW INDEXES FROM mytable;
+---------+------------+---------------------+--------------+-------------+-----------+-------------+----------+--------+------+------------+
| Table   | Non_unique | Key_name            | Seq_in_index | Column_name | Collation | Cardinality | Sub_part | Packed | Null | Index_type |
+---------+------------+---------------------+--------------+-------------+-----------+-------------+----------+--------+------+------------+
| mytable |          0 | UQ_housing_facility |            1 | housing_id  | A         |      500537 |     NULL | NULL   |      | BTREE      |
| mytable |          0 | UQ_housing_facility |            2 | facility_id | A         |      500537 |     NULL | NULL   |      | BTREE      |
| mytable |          0 | UQ_facility_housing |            1 | facility_id | A         |          12 |     NULL | NULL   |      | BTREE      |
| mytable |          0 | UQ_facility_housing |            2 | housing_id  | A         |      500537 |     NULL | NULL   |      | BTREE      |
| mytable |          1 | IX_housing          |            1 | housing_id  | A         |      500537 |     NULL | NULL   |      | BTREE      |
| mytable |          1 | IX_facility         |            1 | facility_id | A         |          12 |     NULL | NULL   |      | BTREE      |
+---------+------------+---------------------+--------------+-------------+-----------+-------------+----------+--------+------+------------+

測試的第一個查詢是相關子查詢-

SELECT SQL_NO_CACHE DISTINCT housing_id
FROM mytable
WHERE housing_id IN (SELECT housing_id FROM mytable WHERE facility_id=4)
AND housing_id IN (SELECT housing_id FROM mytable WHERE facility_id=7);

17321 rows in set (9.15 sec)

+----+--------------------+---------+-----------------+----------------------------------------------------------------+---------------------+---------+------------+--------+---------------------------------------+
| id | select_type        | table   | type            | possible_keys                                                  | key                 | key_len | ref        | rows   | Extra                                 |
+----+--------------------+---------+-----------------+----------------------------------------------------------------+---------------------+---------+------------+--------+---------------------------------------+
|  1 | PRIMARY            | mytable | range           | NULL                                                           | IX_housing          | 4       | NULL       | 500538 | Using where; Using index for group-by |
|  3 | DEPENDENT SUBQUERY | mytable | unique_subquery | UQ_housing_facility,UQ_facility_housing,IX_housing,IX_facility | UQ_housing_facility | 8       | func,const |      1 | Using index; Using where              |
|  2 | DEPENDENT SUBQUERY | mytable | unique_subquery | UQ_housing_facility,UQ_facility_housing,IX_housing,IX_facility | UQ_housing_facility | 8       | func,const |      1 | Using index; Using where              |
+----+--------------------+---------+-----------------+----------------------------------------------------------------+---------------------+---------+------------+--------+---------------------------------------+

SELECT SQL_NO_CACHE DISTINCT housing_id
FROM mytable
WHERE housing_id IN (SELECT housing_id FROM mytable WHERE facility_id=1)
AND housing_id IN (SELECT housing_id FROM mytable WHERE facility_id=3)
AND housing_id IN (SELECT housing_id FROM mytable WHERE facility_id=4)
AND housing_id IN (SELECT housing_id FROM mytable WHERE facility_id=7);

567 rows in set (9.30 sec)

+----+--------------------+---------+-----------------+----------------------------------------------------------------+---------------------+---------+------------+--------+---------------------------------------+
| id | select_type        | table   | type            | possible_keys                                                  | key                 | key_len | ref        | rows   | Extra                                 |
+----+--------------------+---------+-----------------+----------------------------------------------------------------+---------------------+---------+------------+--------+---------------------------------------+
|  1 | PRIMARY            | mytable | range           | NULL                                                           | IX_housing          | 4       | NULL       | 500538 | Using where; Using index for group-by |
|  5 | DEPENDENT SUBQUERY | mytable | unique_subquery | UQ_housing_facility,UQ_facility_housing,IX_housing,IX_facility | UQ_housing_facility | 8       | func,const |      1 | Using index; Using where              |
|  4 | DEPENDENT SUBQUERY | mytable | unique_subquery | UQ_housing_facility,UQ_facility_housing,IX_housing,IX_facility | UQ_housing_facility | 8       | func,const |      1 | Using index; Using where              |
|  3 | DEPENDENT SUBQUERY | mytable | unique_subquery | UQ_housing_facility,UQ_facility_housing,IX_housing,IX_facility | UQ_housing_facility | 8       | func,const |      1 | Using index; Using where              |
|  2 | DEPENDENT SUBQUERY | mytable | unique_subquery | UQ_housing_facility,UQ_facility_housing,IX_housing,IX_facility | UQ_housing_facility | 8       | func,const |      1 | Using index; Using where              |
+----+--------------------+---------+-----------------+----------------------------------------------------------------+---------------------+---------+------------+--------+---------------------------------------+

接下來是我使用GROUP BY ... HAVING COUNT ...的版本

SELECT SQL_NO_CACHE housing_id
FROM mytable
WHERE facility_id IN (4,7)
GROUP BY housing_id
HAVING COUNT(DISTINCT facility_id) = 2;

17321 rows in set (0.79 sec)

+----+-------------+---------+-------+---------------------------------+-------------+---------+------+--------+------------------------------------------+
| id | select_type | table   | type  | possible_keys                   | key         | key_len | ref  | rows   | Extra                                    |
+----+-------------+---------+-------+---------------------------------+-------------+---------+------+--------+------------------------------------------+
|  1 | SIMPLE      | mytable | range | UQ_facility_housing,IX_facility | IX_facility | 4       | NULL | 198646 | Using where; Using index; Using filesort |
+----+-------------+---------+-------+---------------------------------+-------------+---------+------+--------+------------------------------------------+

SELECT SQL_NO_CACHE housing_id
FROM mytable
WHERE facility_id IN (1,3,4,7)
GROUP BY housing_id
HAVING COUNT(DISTINCT facility_id) = 4;

567 rows in set (1.25 sec)

+----+-------------+---------+-------+---------------------------------+-------------+---------+------+--------+------------------------------------------+
| id | select_type | table   | type  | possible_keys                   | key         | key_len | ref  | rows   | Extra                                    |
+----+-------------+---------+-------+---------------------------------+-------------+---------+------+--------+------------------------------------------+
|  1 | SIMPLE      | mytable | range | UQ_facility_housing,IX_facility | IX_facility | 4       | NULL | 407160 | Using where; Using index; Using filesort |
+----+-------------+---------+-------+---------------------------------+-------------+---------+------+--------+------------------------------------------+

最后但並非最不重要的一點是自我加入-

SELECT SQL_NO_CACHE a.housing_id
FROM mytable a
INNER JOIN mytable b
    ON a.housing_id = b.housing_id
WHERE a.facility_id = 4 AND b.facility_id = 7;

17321 rows in set (1.37 sec)

+----+-------------+-------+--------+----------------------------------------------------------------+---------------------+---------+-------------------------+-------+-------------+
| id | select_type | table | type   | possible_keys                                                  | key                 | key_len | ref                     | rows  | Extra       |
+----+-------------+-------+--------+----------------------------------------------------------------+---------------------+---------+-------------------------+-------+-------------+
|  1 | SIMPLE      | b     | ref    | UQ_housing_facility,UQ_facility_housing,IX_housing,IX_facility | IX_facility         | 4       | const                   | 94598 | Using index |
|  1 | SIMPLE      | a     | eq_ref | UQ_housing_facility,UQ_facility_housing,IX_housing,IX_facility | UQ_housing_facility | 8       | test.b.housing_id,const |     1 | Using index |
+----+-------------+-------+--------+----------------------------------------------------------------+---------------------+---------+-------------------------+-------+-------------+

SELECT SQL_NO_CACHE a.housing_id
FROM mytable a
INNER JOIN mytable b
    ON a.housing_id = b.housing_id
INNER JOIN mytable c
    ON a.housing_id = c.housing_id
INNER JOIN mytable d
    ON a.housing_id = d.housing_id
WHERE a.facility_id = 1
AND b.facility_id = 3
AND c.facility_id = 4
AND d.facility_id = 7;

567 rows in set (1.64 sec)

+----+-------------+-------+--------+----------------------------------------------------------------+---------------------+---------+-------------------------+-------+--------------------------+
| id | select_type | table | type   | possible_keys                                                  | key                 | key_len | ref                     | rows  | Extra                    |
+----+-------------+-------+--------+----------------------------------------------------------------+---------------------+---------+-------------------------+-------+--------------------------+
|  1 | SIMPLE      | b     | ref    | UQ_housing_facility,UQ_facility_housing,IX_housing,IX_facility | IX_facility         | 4       | const                   | 93782 | Using index              |
|  1 | SIMPLE      | d     | eq_ref | UQ_housing_facility,UQ_facility_housing,IX_housing,IX_facility | UQ_housing_facility | 8       | test.b.housing_id,const |     1 | Using index              |
|  1 | SIMPLE      | c     | eq_ref | UQ_housing_facility,UQ_facility_housing,IX_housing,IX_facility | UQ_housing_facility | 8       | test.b.housing_id,const |     1 | Using index              |
|  1 | SIMPLE      | a     | eq_ref | UQ_housing_facility,UQ_facility_housing,IX_housing,IX_facility | UQ_housing_facility | 8       | test.d.housing_id,const |     1 | Using where; Using index |
+----+-------------+-------+--------+----------------------------------------------------------------+---------------------+---------+-------------------------+-------+--------------------------+

Answer 2

SELECT housing_id
FROM mytable
WHERE housing_id IN (SELECT housing_id FROM mytable WHERE facility_id=4)
AND housing_id IN (SELECT housing_id FROM mytable WHERE facility_id=7)

Answer 3

您也可以進行自我聯接，最快的聯接將很大程度上取決於表中的數據量。

SELECT a.housing_id
FROM mytable a
INNER JOIN mytable b
ON a.housing_id = b.housing_id AND a.facility_id <> b.facility_id
WHERE a.facility_id = 4 AND b.facility_id = 7